Hitherto, there has been known a phenomenon in which a braking force (braking torque) generated in a vehicle decreases relative to a braking force (braking toque) corresponding to a pressing force of a friction braking member (or a wheel cylinder hydraulic pressure). This phenomenon may be caused by a phenomenon in which a friction coefficient of a friction braking member (brake pad) decreases due to an excess increase in temperature of the friction braking member (so-called fade), a phenomenon in which ice and snow enter between the friction braking member (brake pad) and a disk member (brake disk) to decrease the friction coefficient therebetween (so-called snow fade), or the like. A wheel in which this phenomenon is occurring is hereinafter referred to as “reduced braking force wheel”.
When there is a reduced braking force wheel, required vehicle states (a deceleration state, a turning state, etc.) are difficult to be realized. In particular, in the case where a wheel in which a braking force is generated due to vehicle stability control such as oversteer suppression control or understeer suppression control during the vehicle stability control serves as a reduced braking force wheel, the control is difficult to be achieved because a required turning moment or the like is difficult to be generated.
In order to solve the above-mentioned problem, JP 2009-101918 A describes that, in the case where there is a reduced braking force wheel caused by snow fade, the snow fade of the reduced braking force wheel can be cancelled by performing snow fade cancellation control such as periodically varying a wheel cylinder hydraulic pressure for the reduced braking force wheel greatly or temporarily setting the wheel cylinder hydraulic pressure for the reduced braking force wheel to be an excess high pressure.
Further, JP 2007-237899 A describes that, in the case where there is a reduced braking force wheel caused by fade during anti-lock braking control, an increase in braking distance is suppressed by performing control such as increasing a wheel cylinder hydraulic pressure for the reduced braking force wheel, decreasing a pressure-reducing speed of the wheel cylinder hydraulic pressure, or increasing a pressure-intensifying speed of the wheel cylinder hydraulic pressure.